Telegraphic receiving system



' May 12, 1925. I 1,537,682

G. KRAUSE TELEGRAPHIC RECEIVING SYSTEM Filed Oct. 26, 1920 2Sheets-Sheet 1 May 12, 1925.

G. KRAUSE TELEGRAPHIC RECEIVING SYSTEM 2 Sheets-Sheet 2 Filed OCt. 26,1920 Patented May 12, 1925.

UNITED STATES PATENT OFFICE.

GEORG KRAUSE, OF BERLIN, GERMANY, ASSIGNOB T0 SIEMENS & HALSKE, AKTIEN-GESELLSCHAFT, 0F SIEMENSSTADT, NEAR BERLIN, GERMANY, A GERMAN COB-POBATION.

TELEGRAPEIC RECEIVING SYSTEM.

Application filed October 26, 1920. Serial No. 419,778.

(GRANTEDUNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L,1313.)

To all whom it may concern:

Be it known that I, Gnone KRAUsE, a citizen of the German Empire,residing at Berlin, Germany, have invented certain new and usefulImprovements in Telegraphic accordance with the increase in length ofthe line as well as the increasing distortion of the current curves areso troublesome that it is impossible to go beyond a certain len h ofline, the damping caused by the line ecoming so great that theamplitudes of the current curves do not sufiice any more to actuate thereceiver. If the current impulses tollow each other in rapid succession,the shorter impulses do not fully develop, because they do not attainthe value resulting from the transmitting voltage and the totalresistance.

In order, to amplify such extremely small amplitudes of the currentimpulses it suggests itself to connect in series with the receiver anamplifying device of such ampl fying power that even the smallestamplitudes are amplified sufliciently to actuate the receiver. howeverthe disadvantage that very great amplitudes arriving over the line areamplified to the same degree as the weaker ones, thus causing theformation of secondary amplitudes of such magnitude that the adjustmentof the sensitive receiver is very unfavorabl aflected. For this reasonin such devices eretofore used the smaller amplitudes may be amplifiedonly to a limited degree.

An amplification of such kind has In the receiver system according tothe present invention provided with an amplifier for the transmittingcurrents the small amplitudes can be amplified sufiiciently to securethe actuation of the receiver without this latter being endangered bythe great secondary amplitudes produced by stronger current impulses.This is effected accordmg to the present invention by employing anamplifier having its current amplitudes limited in such a way thattlroseamplitudes which extend to its current limits, suflice to securethe actuation of the receiver, while the secondary amplitudestransgressing such limits are cut otl at the permissible current limits.

Amplification of this sort can be carried out in an especially efiectivemanner with the aid of glow cathode relays with pure electron emission,whose current limits can easily be predetermined by selecting suit ablepotentials for the electrodes, a suitable surface area and temperatureof the glow cathode. One may however employ as well other vacuum tubeamplifiers and devices of a difl'erent kind which may for instance beconnected with current limiting means such as-a highly tempered ironwire, or devices provided with mechanical current limiting means such asfor instance a Brown relay provided with stops.

Owing to the fact that a receiving system according to the presentinvention renders very great amplification possible, a steep- Figure-2shows a receiving system according to the invention to be used inconnection with a double line,

Figure 3 shows the connections for keeping the closed circuit currentoff the relay,

Figure 4 shows a transformer, and

Figure 5 shows a condenser connected in series with the amplifier,

-Fi ure 6 shows a system embodying two amplifiers connected in series.

Referring to Fig. 1 of the drawings, the

effect of the amplifier can be ascertained from the forms of the curvesI, II and III. Supposing a signal composed of positive and negativecurrent impulses be sent out in the form I and to arrive at thereceiving station in the distorted form of curve II, this signal whenamplified would assume the form of the dotted curve III. Thus strongerand weaker amplitudes alternating with each other influence the receiverin a difterent degree. According to the present invention, an amplifieris employed whose secondary current limits are reached at 9,, g,, sothat even in case the grid voltage should rise higher, no greatercurrent is supplied to the receiver, that is to say, all amplitudespassin beyond that point are cut off. There ore the signal transmittedsecondarily by the amplifier assumes about the form of the curve IIIdrawn in full lines which is practically identical with the curve I.Thus a certain regeneration of. the original signals takes place,especially in the case where a very high degree of amplification isresorted to, which may be done quite safely. Y I

A receiving system according to the present invention designed for a,double line is illustrated in Fig. 2. In receiving telegraphic signalsconsisting of direct current impulses it is desirable in many cases topreserve in the received signal the form of the impulses arriving at thereceivingstation as truly as possible. In such telegraph systems where acathode amplifier tube is connected in series with the receiver at thereceiving station it is not possible to attain this end in a simple way,the customary inductive coupling as shown for instance in Fig. 4exerting a strongly distorting action upon the direct current impulsesarrlving at the end of the line. Even a direct connec tion of the linewith the grid and the cathode of the amplifier tube does not furnish theresult desired on account of wave reflections. The system illustrated inFig. 2- allows to obtain a true reproduction of the si nals arriving atthe end of the line by an o mic resistance of suitable dimensionsbridged across the line, such resistance at the same time serving toadjust the zero potential of the grid.

This continuous current grid potential is mamas preferably chosen suchthat it corresponds to the middle of'the linear or straight portion ofthe characteristic curve of the am- ,plifier.

As, shown in Fig. 2, a cathode ray tube V is provided having a hotcathode or filament F, a grid G and a plate or anode P, the filament Fbeing heated by a battery A. The ends of the line connected-to the gridcircuit FG\are bridged by a resistance r, the direct current for thezero potential of the controlling grid being supplied from a battery bthrough aforesaid resistance. The secondary or anode current of the tubemay serve to actuate some suitable receiving device such as a polarizedrelay R whose contacts are marked in the drawing. The same system mightof course be applied to single conductor lines as well, in which theother conductor is formed by the ground.

The secondary current impulses generated by this system further allowthe use of any suitable kind of receiving device since the arrivingimpulses resemble in form the transmitted ones.

Assuming the adjusted armature, resting against one stop contact, isthrown against the otherstop contact by an incoming positive wave, thenit will be thrown again against the first contact at the end of thiswave and remain against this stop contact, while the following negativewave comes in and it will be thrown against the second stop contact atthe end of the negative wave, viz. the beginning of the' next positivewave, as the end of one wave coincides with the be ginning of thefollowing wave.

If it is desired to keep the anode continuous current component,resulting from the battery grid potential, away from the relay, thismaybe effected by means of the system illustrated in Fig. 3 where thereceiver R receives its current from the amplifying device over acapacity K, a resistance R being inserted in the anode circuit inparallel with the receiver. B is the anode battery. With such a devicethe relay R is only affected on changes, but as positive and negativewaves are succeeding one another, the armature is only reversed once foreach impulse. In order to obtain the truest possible reproduction of thesignals through the secondary current impulses care must be taken tomake the time of dying away of the discharge current of the condensor aslong as possible in order to prevent it from falling to zero before theend of the signal. This may be obtained by a sufliciently large capacityK, and a sufiiciently high resistance R.

If a polarized relay is used-as receiver in the system illustrated inFig. 3 the time of dying away of the capacity discharge current can bechosen such that there result only very quick and short current impulseswhich actuate the relay whose armature is reversed in every instance bythe impulses following each other.

In high speed transmission over very long lines it may happen. even withpupinised lines, that owing to the great distortion of the signals shortcurrent impulses such as dots following or proceeding a dash are notdeveloped fully, the grid voltage not going down to the battery currentpotential ofthe grid between two dash-signals. In such a case thearriving signal has the form of a curve as shown at II (Fig. 1).Receiving systems as shown in Figs. 2 and 3 will not serve for signalsof such character. The curve would have the form of the curve drawnin'dots and dashes at III (Fig. 1) and owing to the limitation ofcurrent of the amplifier tube it would furnish the anode or secondarycurrent m n p and in consequence thereof would cause only a singlecontactmaking of the relay instead of five. I

This drawback is obviated by connecting in series with the amplifiertube a transformer U, as shown in Fig. 4. or condensers 2 as shown inFig. 5 in both of which the remainder of the tube connections may be asshown in Figs. 2 or 3. In case a transformer is used the induced currentwill at each reversal of current pass through zero and will thenincrease in an opposite sense. If condensers are provided, at thereversal of current, charges and discharges will alternate. Inconsequence thereof the grid fluctuation will pass at each reversal ofcurrent through the battery potential of the grid and all theamplifiedcurrent alternations and current signals respectively thusattain the zero line, respectively the amplitude of the continuouscurrent amplitude, resulting from the battery grid potential so that nosignal is suppressed. v 7

The use of transformers and capacities further involves the advantagethat in the partial transformation of the impulses the points andcorners which coincide according to curves I, II and II (Fig. 1) andcorrespond to the reversals of current, also coincide with the lines ofintersect-ionof the transformed impulses and thezero line. In the caseof high amplification, therefor, ow-

. ing to the steep rise of the amplified current,

the receiving relay is actuated almost exactly in conformation with thecorners, this being of paramount importance for all devices working insynchronism.

If a plurality of amplifying devices connected in series are used, theconnection illustrated in Fig. 6 is preferably employed. The firstamplifying tube is selected so that all impulses of the amplified cableend current lie within the current limits of the amplifying tube. Thefirst amplifier tube V, is coupled with the second one V over a capacityK, and a resistance R which may be an inductance. In the secondarycircuit of the first amplifier tube is inserted a resistance R Thecurrent fluctuations in its secondary circuit cause fluctuations ofvoltage at the resistance R, and these fluctuations are transferred overthe capacity K to the grid of the amplifier tube V The grid of thelatter receives its direct current potential from a battery I), over theresistance R which must be of sufiicient size to prevent a prematuredying away of the condenser charge. The receiver B may be connected tothe secondary system of tube V in a manner similar to that shown in Fig.3, i. e.. by connecting it to the ends of resistance R by way ofcondenser K All the arrangements described may of course be used also insingle core cables with earth return line. They may further be employedwith advantage for transferring the signals from one cable section tothe other.

I claim 1. The method of receiving telegraphic signals formed of directcurrent impulses which consists in highly amplifying the signals to formsteep current curves and suppressing the apexes of such secondaryamplitudes as might disturb the operation of the receiver before thesaid amplitudes reach the receiver, in limitin the current of saturationof the amplifying tube for amplifying the signals so that the apexes-ofsaid secondary amplitudes are cut off to obtain substantiallyrectangular current curves in said receiver.

2. Receiving system of the kind described comprising in combination acathode ray tube having its primary circuit connected to the line, areceiving device connected in series with the secondary tube circuit, asecondary current in said tube being limited by the choice of anappropriated current of saturation, so that the apexes of such secondaryamplitudes are cut oil, to obtain substantially rectangular currentcurves in said receiver.

3. A receiving system of the kind described comprising in combination anohmic resistance placed across the ends of the receiving line, a cathoderay tube having its grid circuit connected to said resistance, a directcurrent source for impressing a potential to the grid, means forconducting also the direct current derived from said source over saidresistance, said cathode tube adapted to amplify fully the lowestincoming waves, an ohmic resistance inserted in the secondary or anodecircuit of said cathode ray tube, a second cathode ray tube having itsgrid circuit connected to the secondary system of said first mentionedcathode tube, a source of direct current potential applied to the gridof said second tube and a resistance in circuit therewith, a receiverconnected to the secondary system of said second .llt)

tube, the current of saturation of the said second tube being limited soas to cut off the apexes of such secondary amplitudes which mightdisturb the work of said receiver, a resistance inserted in the anodecircuit of said second tube having the receiving apparatus connected toits ends, and a capacity inserted in the connection between the anodecircuit of said first mentioned cathode ray tube and the grid circuit ofsaid second cathode 10 ray tube, a capacity being also inserted incircuit with aforesaid connection of the receiving apparatus.

In testimony whereof I affix my signature.

GEORG KRAUSE.

